Polyolefins are often blended with elastomers in an effort to improve the toughness and processability of a the polyolefin. Various methods of blending polyolefins with elastomers have been explored. In one method, the polyolefin is compounded with bales of elastomer to create a masterbatch. Additional polyolefin are then typically added to the masterbatch at the hopper of an extruder, and the materials are extruded.
Many blends of polyolefins and elastomers have been tried to improve toughness and improve processability. None so far have achieved such.
For example, WO 96/037899 discloses a composition suitable for making the dielectric of a medium-voltage cable comprising, in parts by weight: polymer base, of which at least 50 parts are ethylene copolymer rubber and the balance, if any, polyethylene 100, mineral filler of which at least half is calcined clay 40-120, surface treatment agent for the filler 1-6, zinc oxide 10-30, lead compounds not to exceed 1 calculated as element and appropriate amounts of conventional ingredients comprising an antioxidant, a curing system and a processing aid.
WO 97/000288 discloses a thermoplastic elastomer comprising an elastomeric polymer, a thermoplastic and a curative, wherein the curative is present in the thermoplastic polymer in an amount effective to yield a cure level of the elastomeric polymer of at least 95 percent, preferably at least 97 percent, characterized in that the elastomeric polymer is an ethylene, alpha-olefin, vinyl norbornene, wherein the elastomeric polymer has a Mw/Mn greater than 6, preferably above 10 and wherein the elastomeric polymer has a branching index below 0.6.
WO 98/056012 discloses a cable coating compound based on Superohm 3728, having an electrical dissipation factor less than about 0.6%, a Mooney viscosity of less than about 35 ML (1+8) 100° C., a cure state above about 90 dN·m/min, a tensile strength above about 8.5 MPa, a cure rate above about 100 dN·m/min, and an elongation above about 250%, comprising a) an ethylene, propylene, 5-vinyl-2-norbornene elastomeric polymer having a branching index up to about 0.4, and a Mw/Mn greater than about 10; and b) 5-20 parts per hundred parts of said elastomeric polymer of an ethylene alpha-olefin copolymer having a Mw/Mn less than about 3, a CDBI greater than about 50% and a density in the range of from 0.86-0.92 g/cc. This patent discloses using 5-20 parts per hundred of the ethylene alpha-olefin copolymer.
WO 00/029195 discloses a process for the preparation of a rigid polyolefin article comprising coextruding a polyolefin resin and a friction material resin comprising from 1 to 100% by weight of a friction-increasing material and from 99% to 0% by weight of said polyolefin resin whereby to produce a polyolefin object having an external surface layer of said friction material resin on a substrate layer of said polyolefin resin, and if necessary forming said polyolefin object into said rigid article.
WO 03/068859 discloses a thermoplastic elastomer composition comprising a thermoplastic polyolefin, an elastomer and oil characterized in that it comprises less than 15% by weight of the thermoplastic polyolefin, relative to the total weight of the thermoplastic elastomer composition, the elastomer is peroxide vulcanized and the weight ratio oil/elastomer is above 1.5.
U.S. Pat. No. 5,993,922 discloses a multilayer film having at least one layer of said film containing a PCE composition comprising (i) copolymer having polymeric units derived from (a) at least one polyene monomer, (b) at least one C2-C20 olefinic monomer and, optionally, (c) at least one copolymerizable monomer other than (a) or (b); or (ii) polymer mixture composed of at least one polymer having polymeric units derived from (a) at least one polyene monomer, and at least one polymer having polymeric units derived from (b) at least one C2-C20 olefinic monomer and, optionally, at least one copolymerizable monomer other than (a) or (b); wherein each of at least one layer formed with PCE composition being crosslinked to a greater degree than at least one other layer of said film and wherein at least one layer forming a major surface of the film is sealable. This patent does not teach using more than 10 weight % of the metallocene catalyzed ethylene-propylene-diene monomer.
U.S. Pat. No. 5,932,659 discloses a polymer blend comprising a single-site initiated polyolefin resin having a density below 0.878 g/cm3 and no more than 40 weight percent of a polyolefin including repeating units derived from ethylene and propylene, wherein a portion of the polymer blend is cross-linked and the polymer blend is capable of being formed into a shaped article.
U.S. Pat. No. 6,221,963 discloses a thermoplastic elastomer based on olefin exhibiting the following characteristics (1) to (3): 8.18≦Y−0.43X.≦27, (1) wherein X denotes a JIS A-hardness value of the thermoplastic elastomer based on olefin determined according to the prescription of JIS K 6301, and Y represents a permanent compressive strain value, of the thermoplastic elastomer based on olefin determined according to the prescription of JIS K 6301 under a condition of 70° C.×22 hours, (2) a tensile strength in the range from 5 to 30 MPa determined according to the prescription of JIS K 6301, and (3) a permanent elongation value of 18% or less determined according to the prescription of JIS K 6301.
U.S. Pat. No. 6,723,794 discloses an olefin thermoplastic elastomer composition comprising a crystalline polyolefin resin (A) in an amount of not less than 10 parts by weight and less than 60 parts by weight and an ethylene/alpha-olefin/nonconjugated polyene copolymer rubber (B) which comprises ethylene, an alpha-olefin of 3 to 20 carbon atoms and a nonconjugated polyene in an amount of not more than 90 parts by weight and more than 40 parts by weight, the total amount of said components (A) and (B) being 100 parts by weight, and which is dynamically heat treated to be partially or completely crosslinked, wherein the ethylene/alpha-olefin/nonconjugated polyene copolymer rubber (B) is obtained by randomly copolymerizing ethylene, an alpha-olefin of 3 to 20 carbon atoms and a nonconjugated polyene in the presence of a metallocene catalyst, wherein said polyene contains only one carbon-to-carbon double bond, in one molecule, polymerizable by the metallocene catalyst among carbon-to carbon double bonds, wherein said copolymer rubber (B) has a long-chain branched structure, and has the following properties: (1) said copolymer rubber contains (a) units derived from ethylene and (b) units derived from the alpha-olefin of 3 to 20 carbon atoms in a molar ratio of 40/60 to 95/5; (2) the iodine value is in the range of 1 to 50, in terms of grams based on 100 grams of the copolymer rubber (B); (3) the intrinsic viscosity (η), as measured in decalin at 135° C., is in the range of 0.1 dl/g to 10 dl/g; and (4) the ratio gη* of the intrinsic viscosity (η) of said copolymer rubber (B) determined in the property (3) to the intrinsic viscosity (η)blank of a linear ethylene/propylene copolymer having the same weight-average molecular weight, measured by a light scattering method, as the copolymer rubber (B) and having an ethylene content of 70% by mol, (η)/(η)blank, is 0.2 to 0.95.
U.S. Pat. No. 6,825,253 discloses an insulation composition for electric cable comprising (a) a base polymer comprising at least 20% by weight of ethylene-octene metallocene copolymer; (b) from about 10% to about 60% by weight of a filler; and (c) an additive comprising a blend of; (i) an amine antioxidant, and (ii) at least about 0.5% by weight based on said composition of a hindered amine light stabilizer, wherein the weight ratio of the stabilizer to the antioxidant is greater than 25:75.
US Publication No. 2004/0176540 discloses a vulcanized thermoplastic olefinic rubber composition comprising at least one vulcanizable rubber (A) selected from the group consisting of ethylene-alpha-olefin copolymers, which contain an ethylene unit and a unit of an alpha-olefin having 3 to 20 carbon atoms, and which are produced with use of a metallocene catalyst, and an olefinic resin (B), wherein X and Y as defined below of said (A) are from 1 to 40% and from 0.02 to 0.5, respectively, X=(W2/W0)×100(%) Y=W2/W1 wherein W1 is a weight of a swollen vulcanized rubber (A), which is obtained when (A) in an amount of W0 is extracted with hot xylene, and W2 is a weight measured after drying of the above-mentioned swollen vulcanized rubber (A).
In the above polymer blends, however, the incorporation of a polyolefin increases processability at the expense of toughness, and the incorporation of an elastomer increases toughness at the expense of processability. Additionally, the incorporation of too much of some polyolefins yields blends which are often not cost effective. Accordingly, what is needed are polymer blends that have improved toughness and processability or polymer blends that improve toughness at only a minor expense of processability. Likewise polymer blends having improved processability with no or little reduction in toughness are also desired. Additionally, there is a need for simple and cost effective methods of blending the polymers.